1.- Introduction

2.- MAMI Accelerator

3.- A2 Real Photon Facility

4.- nGDH DAPHNE

5.- Crystal Ball/TAPS/MainzPT

6.- Conclusions and Outlook

NSTAR 2009WORKSHOP ON THE PHYSICS OF EXCITED NUCLEONS

19 - 22 April 2009

Beijing, China Andreas Thomas

A2- and CBall@MAMI- Collaborations

Recent result from the A2 Real Photon Facility at MAMI

Institut für Kernphysik

Beam Parameter (beam since 1990)• 885MeV, E=0.068MeV • max. 103A cw • h=8 nm rad, v=0.5 nm rad (Beam Focus ~m)• Halo: < 10-5 bei r > 5∙r

• ca. 6000h – 7000h operation / year

MAMI B

Parameter (since 2006)• 1507MeV, E=0.100MeV• max. 100A• h=9 nm rad, v=0.5 nm rad• as MAMI B !

MAMI C 1557MeV (since 2008)

zppaNN

NNA bt cos

Determination of the degree of polarization ofthe electron beam (Moeller Polarimeter);Circularly pol. photons

2.

3. Coherent production of linearly polarizedphotons on a diamond radiator

Moeller triggerCoincidence

eE

eE

Electronbeam

Radiator(Moeller target)

Primarybeam%2.01.8 tp

"Vacoflux" Foil

Production und energy measurement of the Bremsstrahlungs photons

A2 Tagging system (Glasgow,Mainz)1.

Polarised Photons @ MAMI C

E = 75 ... 1475 MeV E = 4 MeV N ~ 105 s-1 MeV-1

Data from the GDH experiment @ MAMI B with DAPHNE detector

Detector:Produced by groups from Saclay,Pavia

Proton

Partial reaction channelsInput for PWA to extract resonance parameters

Measurements in 1998 at MAMIwith DAPHNEand Bonn PT

Bonn Polarized target

„Frozen Spin Mode“ Polarization : DNP at high B-Field (2.5 T)

Measurement : very low T )50( mK

´freeze´ up the spin (0.4 Tesla)

relaxation time hT 200

New Technology: horizontal cryostat with integrated solenoid (holding field)

1.2 Kelvin 0.42 Teslaequiv. 780m Cu (100m NbTi)

[C.Bradtke et al., NIM A436, 430 (1999)]Neutron

60 m

m

beam

target

internal superconducting 'ho ld ing coil’liqu id helium from the still

100 m mButanol (C4H9OH)

(C4D9OD)

[Hartmut Dutz, PT Universität Bonn]

[Gerhard Reicherz, PT Ruhr-Universität Bochum]

D-Butanol

Target material [St. Goertz, PT Ruhr-Universität Bochum]

Density and species of the radicals are very important for:

•maximum degree of polarization•polarization build up times

•relaxation timesTrityl-Radikal

Highest Deuteron polarisation due to new doping material with small ESR from Bochum. [W.Meyer et al.]

NN

d

NN

d

NN

d

np0

Reaction channels on deuterium in the MAMI B energy range (< 855MeV):

d

Desintegration

Coherent pion p.

Incoherent pion p.

Coherent eta p.

Incoherent eta p.

Double pion p.

Neutron

Static propertiesof the nuclei:•mass•charge•anomalous magnetic moment

Helicity structureof the deuterons

excitation spectrum

0 100 200 300 400 500 600 700 800 900

-700

-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

0 100 200 300 400 500 600 700 800 900

-600

-400

-200

0

200

400

A.Fix; priv. communication; M.Schwamb et al.; Nucl. Phys. A 696 (2001), 556.

d -> np

d -> pp

d -> nn

coherent d -> pn

-

(b

)

photon energy (MeV)

Sm

edpa

2

22

0

4)()(

Derived 1965 using general asumption:•Lorentz and gauge invariance ->Low energy theorem•causality ->dispersion relation•unitarity ->opt. theorem

[S.B.Gerasimov: Sov.J.Nucl.Phys.2(1966)430][S.D.Drell, A.C.Hearn: Phys.Rev.Lett.16(1966)908]

Gerasimov-Drell-Hearn sum rule (GDH) for nuclei

•Nucleon Nucleon Interaction•Meson Exchange currents •Final State Interaction•Relativistic Effects, Retardation

Model:

0 100 200 300 400 500 600 700 800 900

-700

-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

0 100 200 300 400 500 600 700 800 900

-600

-400

-200

0

200

400

A.Fix; priv. communication; M.Schwamb et al.; Nucl. Phys. A 696 (2001), 556.

d -> np

d -> pp

d -> nn

coherent d -> pn

-

(b

)

photon energy (MeV)

[H. Arenhövel, et al., Phys. Rev. Lett. 93 (2004) 202301]

IGDH= 0.65b

Helicity dependent deuteron photodesintegration[Arenhövel et al. , Physics Letters B 407 (1997) 1-7]

(1232)-resonance(Spin3/2)

The resonance can better be excited if the inital spins are parallel at 300MeV

proton (neutron)(Spin 1/2)

uud

„Flip of a single quark“:p >> a

a >> p

photon (Spin 1)

photon (Spin 1)

P N3S1 deuteron ground state

(Spin 1)

P N1S0 resonant state at 68KeV

(Spin 0)The resonant 1S0 state can only be reached if the inital spins are

antiparallel at energies close to break-up threshold (2-3MeV)

Phys. LettersB 672(2009)328-332

New precission data set to determine the deuteron-GDH-sumrule above -threshold [Phys. Letters B 672(2009)328-332

Model AFS

Partial reaction channels and polarisation observables deliver more informationto improve the deuteron models and our knowledge on the neutron.(Better Models are needed.)

Sm

edap

2

22

0

4)()(

Gerasimov-Drell-Hearn sum rule (GDH) for nuclei

Photon Nucleon

1 S

a

p

Deuteron

3Helium

P N

P P N

P(Neutron) ~ 0.92 P(Deuteron)

..exp effnuclpGDH

nGDH

d IIII

'..exp effnucl

pGDH

nGDH

he IIII 1.0

Partial reaction channels on

quasifree neutron

GDH-Integralwith small

systematic error

IGDH [b]

proton 204

neutron 233deuteron 0.653helium 497

Deuterated Butanolwas used as target material in 98 (pilot exp.) and 2003

New Exp. In May 2009 on 3Helium

[W.Heil, J.Krimmer, P.Bartolomez]

4 photon Spectrometer @ MAMI

TAPS:364 BaF2 detectorsMax. kin. energy:+- : 180 MeVK+- : 280 MeVP : 360 MeV

Crystal Ball:672 NaJ detectorsMax. kin. energy:+- : 233MeV+- : 240 MeVK+- : 341 MeVP : 425 MeV

Vertex detector:2 Cylindr. MWPCs480 wires, 320stripes

PID detector:24 thin plastic detectors

Crystal Ball / TAPS

Transverse

And

Longitudinal

Internal

Holding coil

Polarized Target for Crystal Ball

Tagged CW photon beam 4- detector

Frozen spin target (20mKelvin, 5Tesla)Pproton ~ 95%Pdeuteron~70%All directions of polarization

sec107

New 3He4He-Dilution refrigerator(in collaboration with JINR Dubna)

High Field 1T

Threshold Production

Transverse Field

Beam Target

Photoproduction with polarized beam and polarized target

EPGPP

PPTP

FPHPP

Pd

d

d

d

circlinz

liny

circlinx

lin

unpol

2sin

2cos

2sin

2cos1

EGP

PTP

FHP

dd

P

PPP

z

y

x

unpol

circlinlinunpol

- -

- -

- -

- -

4,

4

2,0 Target

Beam

+ Recoil observables [D.Watts, M.Sikora] Wed.,Session6

Conclusion and Outlook

Data from ‚Crystal Ball‘ detector in combination with TAPS and further detectors at MAMI B (882MeV) and MAMI C (1557MeV) are under analysis. Publications 2009:Dalitz Plot Parameter 0η-production, Measurement -mass, rare -decaysMDM, Helicty asymmetries

MAMI C is delivering polarised beam with now 1557 MeV and high Intensity for the experiments since 2008

New precission data set from the neutron-GDH-experiment with ‚DAPHNE‘ detector and is published [Phys. Letters B 672(2009)328-332]Paper on Helicity Dependent Deuteron Photodisintegration between 160 and 480 MeV and single pion production up to 800 MeV is under preparation.

Future: In A2 we continue to do double polarised experiments with polarised beam, polarised targets (3Helium 5/2009 H,D-Butanol 12/2009) and recoil-polarimeter.

Neutron (D,3He)

Theoretical description

Proton (Frozen Spin)

Threshold, Transverse, Complete exp.

Helicity Dependent Deuteron Photodisintegration between 160 and 480 MeV to be submitted EPJA

Crystal Ball @ MAMI Collaboration

Run 2004/2005 700 Stunden Tests3600 Stunden Datennahme

12 PhD

The GDH collaborationJ.Ahrens9,S.Altieri15,16,J.R.M.Annand6,G.Anton3,H.-J.Arends9,K.Aulenbacher9,R.Beck9, C.Bradtke1,A.Braghieri15,N.Degrande4, N.d'Hose5, H.Dutz2, S.Goertz1, P.Grabmayr17, K.Hansen8, J.Harmsen1, S.Hasegawa13,T.Hasegawa11, E.Heid9, K.Helbing3, H.Holvoet4, L.VanHoorebeke4, N.Horikawa14,T.Iwata13, P.Jennewein9, T.Kageya14, B.Kiel2,F.Klein2, R.Kondratiev12,K.Kossert7,J.Krimmer17,M.Lang9,B.Lannoy4,R.Leukel9,V.Lisin12,T.Matsuda11,J.C.McGeorge6,A.Meier1,D.Menze2,W.Meyer1,T.Michel3,J.Naumann3, A.Panzeri15,16, P.Pedroni15,T.Pinelli15,16,I.Preobrajenski9,12,E.Radtke1,E.Reichert10,G.Reicherz1,Ch.Rohlof2, G.Rosner6, D.Ryckbosch4,F.Sadiq6,M.Sauer17,B.Schoch2, M.Schumacher7, B.Seitz7, T.Speckner3,M.Steigerwald9, N.Takabayashi13, G.Tamas9, A.Thomas9, R.van de Vyver4, A.Wakai14, W.Weihofen7, F.Wissmann7, F.Zapadtka7, G.Zeitler3

1Institute of Experimental Physics, Ruhr-University, Bochum, Germany 2 Physics Institute, University of Bonn, Germany 3 Physics Institute, University of Erlangen-Nuernberg, Erlangen, Germany 4 Nuclear Physics Laboratory, Gent, Belgium 5 CEA Saclay, DSM/DAPNIA/SPhN, Gif-sur-Yvette, France 6 Department of Physics & Astronomy, University of Glasgow, U.K. 7 II.Physics Institute, University of Goettingen, Germany 8 Department of Physics, University of Lund, Sweden 9,10 Institute of Nucl. Physics and Inst. of Physics, University of Mainz, Germany 11 Faculty of Engineering, Miyazaki University, Miyazaki, Japan 12 INR, Academy of Science, Moscow, Russia 13,14 Department of Physics and CIRSE, Nagoya University, Nagoya, Japan 15,16 INFN Sezione di Pavia and Dept. of Nucl. Physics of the University , Pavia, Italy 17 Physics Institute, University of Tuebingen, Germany

Data set with high statistics for and production [F.Zehr, S.Schumann]

p p00

Rot TAPS DatenKurven:ChPT

Excitation Spectrum of the nucleonPion Production Eta Production

polarisation observables essential

Strahl Target

Photoproduction of pseudoscalar ‘, K with polarised beam and target

EPGPP

PPTP

FPHPP

Pd

d

d

d

circlinz

liny

circlinx

lin

unpol

2sin

2cos

2sin

2cos1

EGP

PTP

FHP

dd

P

PPP

z

y

x

unpol

circlinlinunpol

- -

- -

- -

- -

4,

4

2,0 Target

Beam

Pion Photoproduction with Polarized Beam and Polarized Target

N N

1 NlL l

Angular momentum and parity conservation

)()()( NJRJNJ PPP

Parity

Multipole components of the electromagnetic radiation

EL, ML

21

21 lJL

lL

lL

lL

lL

11

1

)1()1(

1)1()1(EL :

ML :

Multipole amplitudes:

llll MMEE ,,,

21lJ

21lJ

ll ME ,JIl 2,2

Angular momentum

Connection between and andMultipoles and Resonances

21 2

3

1 lL

21

23

............2*

221

11*

110

}Re{6

}Re{638

22

222

MEEM

MMEEE

kq

Photon Photon Total Pion Multipole Resonance ContributionL Multipole J P l Amplitude to

1 E1 1/2 - 0 E0+ S11 -

3/2 - 2 E2- D13 +

M1 1/2 + 1 M1- P11 -

3/2 + 1 M1+ P33 +

2 E2 3/2 + 1 E1+ P33 -

5/2 + 3 E3- F15 +

M2 3/2 - 2 M2- D13 -

5/2 - 2 M2+ D15 +

N N

l

JIl 2,2

-prod.->Deformation

p p

E[MeV]

b]

MAID2000

[Phys. Rev. Lett. 84, 5950 (2000)]

200 300 400 500

0

50

100

150

200

250

300

350 -2.5% 0% +2.5% GDH98

p n

E[MeV]200 300 400 500

-150

-100

-50

0

50

100

150

200

-2.5% 0% +2.5% GDH98

[Phys. Rev. Lett. 88 (2002) 232002]

2nd Resonance regionD13Resonance Parameters 20% changed

Connection between and andMultipoles and Resonances

21 2

3

1 lL

21

23

............2*

221

11*

110

}Re{6

}Re{638

22

222

MEEM

MMEEE

kq

Photon Photon Total Pion Multipole Resonance ContributionL Multipole J P l Amplitude to

1 E1 1/2 - 0 E0+ S11 -

3/2 - 2 E2- D13 +

M1 1/2 + 1 M1- P11 -

3/2 + 1 M1+ P33 +

2 E2 3/2 + 1 E1+ P33 -

5/2 + 3 E3- F15 +

M2 3/2 - 2 M2- D13 -

5/2 - 2 M2+ D15 +

N N

l

JIl 2,2